In an optical communication system, it is generally necessary to couple an optical fiber to an opto-electronic transmitter, receiver or transceiver device and to, in turn, couple the device to an electronic system such as a switching system or processing system. These connections can be facilitated by modularizing the transceiver device. Such optical transceiver modules include a housing in which are mounted opto-electronic elements, optical elements, and electronic elements, such as one or more light sources (e.g., lasers), light sensors (e.g., photodiodes), lenses and other optics, digital signal driver and receiver circuits, etc. In addition, a transceiver module typically includes an optical connector that can be coupled to a mating connector at the end of a fiber-optic cable. Various optical transceiver module configurations are known. For example, an optical transceiver module having an elongated housing with a rectangular cross-sectional shape, where the rear of the module plugs into a bay of a front-panel cage and the front of the module accepts an optical fiber plug, is commonly referred to as Small Form-Factor Pluggable or SFP.
An optical transceiver module or other optical communication module that has a plurality of similar opto-electronic devices that are operable in parallel, such as a plurality of lasers or a plurality of photodiodes, is commonly referred to as a parallel optical communication module. Differential thermal expansion among the opto-electronic elements (e.g., lasers or photodiodes), substrates, lenses, lens mounts, and other elements in the optical signal paths can impair proper module operation. More specifically, in response to an increase in temperature, elements in the optical signal path that are made of materials having different coefficients of thermal expansion (CTE) move different amounts with respect to each other. For example, as illustrated in FIGS. 1A-B with respect to a three-axis (x, y, z) frame of reference (also known as a Cartesian coordinate system), a monolithic parallel laser chip 10 having a gallium arsenide or similar substrate can expand and contract to a different extent in the x-axis direction than a parallel plastic lens array 12 in which each laser 14 of chip 10 is intended to be optically aligned with one of the lenses 16 of lens array 12 to define an optical signal (beam) path 18. If such differential expansion occurs, any given one of the lasers 14 and the corresponding one of lenses 16 can become misaligned, i.e., no longer aligned on the intended optical signal path 18, from each other. To inhibit the detrimental effects of differential thermal expansion, such elements are commonly made of materials having as similar CTEs to each other as possible. For example, modules having gallium arsenide laser chips commonly include glass or quartz lens arrays rather than plastic lens arrays because the CTEs of glass and quartz are closer to the CTE of gallium arsenide than the CTE of plastic is to the CTE of gallium arsenide. However, it would be desirable to use plastic lenses instead of glass or quartz lenses because plastic lenses are more economical than glass or quartz lenses.